Plug and dead end receptacle



A ril 1 2, 1938. N. A. TORNBLOM PLUG AND DEAD END RECEPTACLE Filed April 1, 1936 2 Sheets-Sheet 1 I A ril 12, 1938. N, A, ORN OM 2,114,258

PLUG AND DEAD END RECEPTACLE Filed April 1, 19:56 2 sheets-sneeiz glifiwllllllllllll llm i J Z9 III Patented Apr. 12, 1938 PATENT OFFICE 2,114,258 PLUG AND om nun nnonr'rncnn Nils A. Tornblom, Chicago, Ill., aasignor to Appleton Electric Company; a corporation of Illinois Application April 1, ms, Serial No. 72,045

2 cums. .(01. 173-328) The present invention may be said to have two main objects which are, first, to provide the receptacle member of a separable connector with means to dead-end" it upon the separationv of the plug member therefrom; and, second, to break the electrical connections within enclosed spaces or'chambers, whereby the formation of arcs cannot cause the ignition of gases surrounding the device as a whole.

In carrying out my invention I so construct and arrange the cooperating contact elements that the arcs formed upon the withdrawal of the plug member will be broken before they can be reached by outside gases, and provide the receptacle with a shield that normally covers and conceals the contact elements in the receptacle; the cover or shield being provided with openings through which the contact elements on the plug must pass to reach the cooperating elements in the receptacle; and making it necessary that the shield be moved from its normal protective position, after the contact elements on the plug have been entered in the openings therein, to bring such openings into registration with the contact elements in the receptacle. Thus, the

plug goes through three steps in making a connection, the first step being that of engaging its contact elements in the openings in the shield, the second step being that which causes the shield to be moved from its normal position, and the third step being that which permits the contact elements to be brought into engagement with-the contact elements in the receptacle. Means are also provided to prevent the complete withdrawal :5 of the plug from the receptacle, excepting through these same three .steps, carried outiin the reverse order, however. The shield gives the "dead end" effect to the receptacle upon the removal of the plug, and the provision for compelling the'three-step movements of the plug insuresthat arcs will be extinguished within the receptacle and without possibility of access to the surrounding atmosphere.

The various features of novelty whereby my in- 48 v'ention is characterized will hereinafter be on connection with the accompanying wherein:

Figure 1 is a view, partly in side elevation an partly in section, of a receptacle and plug embodying the present invention. in coupled rela- 53 tlon; Fig. 2 is a section on line 1-2 of Fig. 1,

parts of the shield and of the plug being broken away, and the shield and the plug being shown in the positions whichthey occupy at the end of the first step in making a connection instead of at the end of final step as in Fig. 1; Fig. 3 isa section on line H of Fig. 1, showing the parts in the same positions which they occupy in Fig. 1; Fig. 4 is a section on line 4-4 of Fig. 3; Fig. 4a is a view of a portion of Fig. 4 on an enlarged scale with the plug and receptacle in a different position; Fig. 5 is an elevation of one end of the plug member; Fig. 6 is a section taken on line 7 6-4 of Fig. .3; Fig. 'I is a section taken on line 1-] of Fig. 4; and Fig. 8 is a rear view of the rotatable shield in the receptacle, removed from the latter. v

In the drawings Ihave illustrated only a single preferred embodiment of my invention and shall confine the detailed description to that particular embodiment; it being understood that the principle of the invention may be employed in forms or constructions differing greatly in detail from the particular construction illustrated.

In the drawings, l is a sturdy body of insulating material, the main portion of which is in the form of a cylindrical block. At one end of the cylindrical portion of the member I are diametrically opposed thick lugs or ears 2. .The member I is supported from a member 3 which may be a strong face plate, boxcover or a housing or a portion of a housing. The insulating block in diameter than the external diameter of the cylindrical block.

The member i has a plurality of passages extending throughout the length thereof, these passages being parallel to and spaced at equal distances from the central axis of the member I. In the arrangement shown, there are four of these passages, each indicated by the reference numeral I. The rear end of each of the passages :1 is enlarged in diameter and contains a stationary contact in the form of a metal sleeve 8 fitting tlghtlytherein; the internal diameter of the sleeves being equal to the diameter of the 'front ends of the 'paaages I. Each of the stationary contacts is connected to aicorrespon'ding terminal 9 mounted on the inner or rear end of the member l.

Resting against the front end or face of the member I is a thick disk H of insulating material of the same diameter as the cylindrical part of the member 6. The disk has on the rear or inner side a cylindrical hub I2 that fits rotatably in a recess or socket H in the front end of the member The disk is held to the member I, while rotatable thereon, by a shaft or stem ll extending throughout the length of the member I at the central axis of the latter and having at the forward end a screw-threaded part l5 that engages with a nut l6 molded in the disk or shield II; The rear end of the shaft or stem ll lies in an enlarged chamber ll, in the member I.

A collar i8 on the shaft or stem l4 engages with the wall at the forward end of the chamber I'I and'serves to prevent lengthwise movement of the shaft or. stem in the forward direction, while the disk or shield ll prevents the shaft or stem from being withdrawn in the rearward direction untilv it is unscrewed from the disk or shield. Surrounding the rear end of the shaft or stem I4, withinthe chamber 91, is a torsion spring l9 one end, 2!, of which is engaged in a slot 22 in the shaft or stem and the other end of which, 23, is entered into a longitudinal groove 24 cut into one wall of the chamber Ill. 0n the rear side of the disk or shield ll, adjacent to the periphery, is a segmental lug 25 projecting into a segmental notch 26 in the front end of the member I. Consequently, the shield or disk can turn through an annular distance determined by the proportions of the lug 25 and the notch 26. The spring i9 is under an initial tension and tends constantly tohold the lug 25 at one end of the notch 26, namely the righthand end as viewed in Fig. 7. The disk or shield H has four round openings 21 extending through the same parallel with the longitudinal axis of the device. These openings arev of the same diameter as the forward ends of the passages l in the member I, and they are correspondingly located with respect to the longitudi- .l and these passages are covered by solid portions of the shield. At this time the lug 25 is in engament with a wall or shoulder at the righthand end of the notch 28. Thus, access to the stationmy contacts 8 is entirely cut oil from the front of the receptacle. When the shield is turned in the clockwise direction through an angle of 45, the openings 21 are brought into registration with the passages l, and contact fingers may be passed through the openings 21 and the forward ends oi the passages l and be engaged 'with the stationmy contacts 2. 1

Ihe plug member that cooperates with the receptacle may he of any suitable form. In the arrangement shown, it comprises a long, cupshaped casing 28 whose open end is of the same external diameter as the internal diameter of the tubular hub 5, so that the casing may be inserted in the hub. Theinternal diameter of the plug casing is slightly greater than the external diameters of the shield and'the cylindrical portion of the member I so that, when the plug casing is inserted in the hub, it surrounds the shield' the forward edge of the hub and limiting the extent of entry of the plug device into the receptacle. The interior of the plug casing, for a distance inwardly from the open end somewhat greater than the distance to which the member l and its shield are designed to enter the casing when a connection is made, is left unobstructed, except for the presence of four long contact fingers 3| arranged parallel with the long axis of the device and located with respect to that axis in a manner to correspond with the locations of the openings 21 and the passages 7.

With the shield II in its normal position, as shown in Fig. 2, upon aligning the contact fingers 3| with the openings 21, the plug device may be partially entered into the receptacle. Even if no tact fingers therein, are brought into alignment with the passages l in the member l shown in Fig. 7. Now the plug may be pushed in until the contact fingers enter the tubular stationary contacts 8, as shown in Fig. 4.

It is advisable that the casing of the plug device be interlocked with the shield in addition to the interlocking due to the presence of the contact fingers in the openings 27, so that the contact fingers are not subjected to the duty of turning the shield. It is also desirable that the casing of the plugdevice be interlocked with the member 3 of the receptable or its hub, so that the contact fingers may not be withdrawn from the shield except when the latter is in its normal position in which it dead-ends the receptacle. The interlocking of the plug casing with the rotatable shield, for driving purposes, may be conveniently. accomplished by providing the shield with a peripheral notch 32 adapted to be engaged by the 4 head 33 of a rivet passing through and fixed in the tubular wall of the casing near the open end'of the latter, as best shown in Figs. 2, 6 and 8; When it is desired 'to insert the plug into the receptacle, the rivet head is aligned with the notch or groove 32, at which time the contact fingers are aligned with the openings 27, as indicated inFig. 2. Upon turning the plug, the rivet head acts as the driving member for tuming the shield. So that there will be no obstruction in the path of the rivet head when the plug is finally pushed home into the receptacle, the

cylindrical portion of the member 5 is provided of the plug and the receptacle may conveniently consist of a Z-shaped groove 35 in the periphery of the plug casing; this groove comprising a long longitudinal portion extending from the flange 29 to within a short distance of the open end of the casing, a circumferential section extending from the front or outer end of this long leg parallel with the front edge of the casing, and

then a short leg extending in the longitudinal 2,114,258 direction and opening out through the edge of the casing at the open end of the latter, as best shown in Fig. 5. Cooperating with the groove 35 is the head 36 of a rivet fixed in the wallof the tubular hub 5, as best shown in Figs. 1 and 2. The parts are so located that the plug can be entered in the hub of the receptacle only when the short longi- Q tudinal leg of the groove 35 is brought into registration with the rivet head 36, at which time the rivet head 33 is in registration with the groove or notch 32 in the shield, and the contact fingers 36 are aligned with the openings 21 in the shield. Therefore, in making a connection, the plug and the receptacle are properly aligned through the rivet head 36 and the inlet end of the groove 35, whereupon the plug may be pushed in until it is interlocked with the rotatable shield; then the plug may be turned, carrying the shield along with it until the openings 2'5 are aligned with the passages i as in Fig. 4a; and, finally, the plug may be pushed in so as to engage its fingers with the stationary contacts in the receptacle, as in Fig. 4; all three of these movements of the plug being under the guidance of the pin and groove connection between the plug casing and the tubular hub or the receptacle.

After a connection has been completed, the separation of the plug from the receptacle can be effected only by reversing the three-step movement of the plug; the first step consisting in withdrawing the plug lengthwise through the long longitudinal leg of the Z-shaped groove, which results in drawing the contact fingers of the plug out of engagement with the stationary contacts and far enough away from the latter, as in Fig. 4a, to insure that any arcs that are created between the separating contact elements will be extinguished. This straight lengthwise movement must of course carry the contact fingers out far enough so that they are entirely clear of the member I and thus make it possible for the protective shield to be turned. After the plug has been withdrawn to the extent just described, it may be rotated to shift the contact fingers from the relative angular positions which they occupy in Fig. 3 to the angular positions of Fig. 2; this angular movement being limited by the length of the circumferential section of the groove 35 and causing the ends of the passages I in the member I to be completely covered as in Fig. 2. The final withdrawal of the plug is permitted bythe shortleg of'the groove 35, and serves simply to withdraw the plug completely from the receptacle and the rotary shield which then remains in its normal protective position, being held there by the spring.

Since the rotatable disk or shield H is not intended to take the place of the ordinary door or cover, with which receptacles are often provided, any usual or suitable door 31 may be mounted on the receptacle in position to extend across the open end of the tubular hub and close the same when the plug is withdrawn.

It is advisable effectively to ground the external metal parts of the plug when operatively engaged with the receptacle. To this end I have arranged in a longitudinal peripheral groove a in the periphery of the cylindrical body portion of the member I, which also continues as .a tunnel through one of the lugs 2, a spring finger a. one end of which may conveniently be held in place bytbescre'wll thatfastensthelugto the corresponding bracket H. The free end of this spring finger is adapted to project slightly beyond the periphery of the cylindrical part of the member 5 and be so shaped that when the plug is inserted, the finger enters the open end of the plug casing and is pressed down into the groove more or less, thereby causing it to make a good, wiping contact with the inner surface of the surrounding casing. This spring finger may be grounded through the screw, the bracket and the casing or housing for. the receptacle, or in any other suitable manner. Also, if desired, the grounding devices just described may be provided in duplicate, as illustrated in Fig. 1.

it will thus be seen that I have produced a simple and novel construction in' which one of the members of a plug and receptacle combination is automatically dead-ended upon separation of such member from each other, in which the arcs created in breaking the circuits are formed and extinguished in closed chambers and cannot set to ignite combustible gases in the atmosphere While I have illustrated and described with particularity only a single preferred form of my invention, I do not desire to be limited to the exact structural details thus illustrated and described; but intend to cover allforms and arrangements which come within the definitions of my invention constituting the appended claims.

I claim:

1. In combination, a receptacle and a plug separable from each other by relative lengthwise movement, contacts in the receptacle, a rotatable shield of insulating materialin front of said contacts and adapted in one angular position to cover the same, said shield having openings adapted in a second angular position to register with and expose said contacts, contact fingers on the plug adapted to be inserted through said openings and then be engaged with said contacts by a lengthwise movement while the shield is insaid second angular position, and interlocking shoulders on the receptacle and the plug to compel the plug to move with the shield into the first of the said angular positions of the latter before the contact fingers on the plug can be withdrawn from the openings in the shield after a connection has been made. I

2. In combination, a receptacle and a plug separable therefrom, said receptacle including a body member of insulating material having passages extending into the same through the front face, contacts in said passages, a shield of insulating material engaged with the front face of said body member, means to support said shield for angular movements on said body member, said shield having openings therein which in one position of the shield register with said passages and in a second position of the shield leave said passages covered by the shield, spring means tending constantly to hold said shield in said second position, contact elements on the plug adapted to be. inserted'through said openings and to enter said passages and be engaged with said contacts, and shoulders on the shield and the plug interlocking with each other to hold them against relative rotary movements while the said fingers are engaged in said openings and clear of said runs a TORNBLOM. 

